CRYSTAL-STRUCTURE OF PVUII ENDONUCLEASE REVEALS EXTENSIVE STRUCTURAL HOMOLOGIES TO ECORV

The crystal structure of the dimeric PvuII restriction endonuclease (R .PvuII) has been determined at a resolution of 2.4 Angstrom. The prote in has a mixed alpha/beta architecture and consists of two subdomains. Despite a lack of sequence homology, extensive structural similaritie s exist between one R.PvuII subdomain and the DNA-binding subdomain of EcoRV endonuclease (R.EcoRV); the dimerization subdomains are unrelat ed. Whithin the similar domains, flexible segments of R.PvuII are topo logically equivalent to the DNA-binding turns of R.EcoRV; potential ca talytic residues can be deduced from the structural similarities to R. EcoRV. Conformational flexibility is important for the interaction wit h DNA. A possible classification of endonuclease structures on the bas is of the positions of the scissile phosphates is discussed.